1. Field of the Invention
This invention generally relates to an electronic device, and more particularly to a semiconductor chip package and a manufacturing method thereof, wherein a semiconductor die is encapsulated by a plastic package body in a manner that the backside surface of the die is exposed through the plastic package body.
2. Description of the Related Art
FIG. 1 depicts a conventional semiconductor chip package including a lead frame for supporting a semiconductor die 100. The lead frame includes a plurality of leads having outer lead portions 106 and inner ends 107. The die 100 is attached onto a die pad 111 by means of a silver paste 114. The die pad 111 is connected to the lead frame by supporting bars (not shown in FIG. 1). The outer lead portions 106 are used for electrical coupling to an outside circuit. The die 100 has bonding pads 117 electrically interconnected to the inner ends 107 of the lead frame though bonding wires 115. The die 100, the die pad 111, the inner ends 107 of the lead frame and bonding wires 115 are encapsulated in a plastic package body 116 made of insulating material such as epoxy.
Because the plastic package body 116 completely surrounds the die 100, the heat generated from the die 100 during normal operation must pass through the package body 116 to outside. Due to the insulating properties of the package body 116, heat dissipation from the die 100 is resisted, thereby creating, in some instances, high temperatures within the conventional package which might impair or damage the die 100.
It is a primary object of the present invention to provide a semiconductor chip package comprising a lead frame having a window pad for the supply of ground potential and a die enclosed in a plastic package body, wherein the lower surface of the lead frame and the backside surface of the die are exposed through the plastic package body for improving the thermal performance of the semiconductor chip package.
It is another object of the present invention to provide a semiconductor chip package comprising a lead frame and a die enclosed in a plastic package body, wherein predetermined portions of the surface of the lead frame are provided with a cupric oxide coating for enhancing the adhesion between the lead frame and the plastic package body.
A semiconductor chip package in accordance with a preferred embodiment of the present invention generally comprises a lead frame, a semiconductor die and a plastic package body. The lead frame includes a window pad having an opening defined therein and a plurality of leads having inner ends defining a central area. The window pad is connected to the lead frame by connecting bars and disposed within the central area. The semiconductor die is disposed in the opening of the window pad and has a plurality of bonding pads formed on the active surface thereof. The inner ends of the leads are interconnected to the bonding pads on the semiconductor die through a plurality of bonding wires. The plastic package body encapsulates the lead frame, the semiconductor die and the bonding wires wherein the lower surface of the lead frame and the backside surface of the semiconductor die are exposed through the plastic package body.
Since the lower surface of the lead frame and the backside surface of the semiconductor die are exposed through the plastic package body, the heat generated from the die during normal operation can be directly dissipated by convection and radiation from the backside surface of the die and the lower surface of the lead frame to the surrounding air and the outside environment thereby enhancing the thermal performance of the semiconductor chip package of the present invention.
In a semiconductor chip package in accordance with another preferred embodiment of the present invention, the lead frame has a cupric oxide coating formed on the predetermined portions of the surface thereof. Since the cupric oxide coating has a contour of roughness, the bonding mechanism of the interface between the cupric oxide coating and the plastic package body includes chemical bonding as well as mechanical interlock thereby greatly enhancing the adhesion between the lead frame and the plastic package body. Accordingly, the probability of delamination of the metal-plastic interface is significantly reduced such that the moisture from surrounding can be prevented from directly diffusing through the exposed bond line between the lead frame and the package body into the semiconductor chip package.
The present invention further provides a method for producing a semiconductor chip package comprising the steps of: (A) attaching a adhesive tape to a surface of a lead frame in a manner that an opening of a window pad of the lead frame is covered by the adhesive tape; (B) attaching a semiconductor die to the adhesive tape within the opening of the window pad; (C) electrically coupling the semiconductor die to the lead frame; (D) encapsulating the lead frame and the semiconductor die in a plastic package body; and (E) removing the adhesive tape to expose a lower surface of the lead frame and the backside of the die.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.